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Trochoidal milling has been developed to enhance tool life during slot machining. It is characterized by reduced cutting forces, cutting temperature, and tool wear as compared to conventional milling processes. It is effective in machining difficult-to-cut materials, high-speed machining, and groove corners. However, this process has not been deeply investigated enough to discover its advantages and optimize its parameters. A full factorial design of 144 experiments has been applied in this paper to investigate extensively the effects of axial depth of cut, feed rate, and trochoidal step on material removal rate, cutting forces, and specific energy in trochoidal milling. Trochoidal step and axial depth of cut almost have the same contributions on cutting forces by 32% and 31% respectively, followed by feed rate by 25%. Feed rate, trochoidal step, and axial depth of cut influence the material removal rate by 37%, 30%, and by 19% respectively. The contributions of feed rate, trochoidal step, and axial depth of cut on relative specific energy are 57%, 24%, and 8% respectively. The increase of axial depth of cut increases the maximum resultant force till a threshold value, then it stabilizes. This behavior occurred due to the increase of the maximum engagement angle to a certain limit, then it does not increase any more. Both feed rate and trochoidal step linear affect maximum resultant force and material removal rate, while the relationships are non-linear for specific energy. It is recommended to machine slots in full depth with the highest possible trochoidal step and feed rate, considering the increase of tool wear and surface roughness. It is preferred to use a cutting tool of a large helix angle and small diameter to reduce the threshold axial depth of cut. Overall, this study is significant in characterizing, designing, and optimizing of trochoidal milling through experimental work.

With the rapid development of the flexible electronics field, flexible pressure sensors are widely used inwearable devices, medical monitoring and other fields. However, it is still a huge challenge to design a sensor with highsensitivity, low cost and a simple manufacturing process. In this work, we report a flexible strain sensor based on discarded mask straps (MS) with a unique three-dimensional (3D) twist-like network structure. Multi-walled carbon nanotubes (MWCNTs)/carbon nanoparticles (CN)/MS composites were prepared by a simple dip-drying method and encapsulated using a medical Polyurethane (PU) film. It is founded that the fabricated MWCNTs/CN/MS/PU flexible strain sensor (MCMP-FSS) exhibits a high gauge factor (GF) of 13,928 and advanced performance with a large sensing range of 0%–72%. Moreover, good water-repellent harmony and various types of stimuli over 1000 cycles were obtained for the MCMP-FSS. Benefiting from the unique 3D twist-like network structure and the MWCNTs/CN synergistic conductive network, MCMP-FSS also has broad application prospects in the fields of human motion detection, encrypted communication, and natural human-robot interaction.

This paper presents a steady state cutting force prediction model for CNC lathe considering feed displacement. The frequency spectrum characteristics of the cutting force in principal direction are analyzed. The turning test for 12Cr18Ni9 stainless steel workpiece is carried out by CNC machine tool ETC1625P firstly, and the real-time displacement data of worktable in the turning process are obtained. The cutting force data varying with the displacement of the worktable under different cutting parameters are obtained by cubic spline interpolation. The mechanical force model including metal shearing force and plowing force is established, so as to predict the steady state cutting force accurately corresponding to different displacement of the worktable. The influence of different cutting parameters on the amplitude frequency characteristics for the low frequency part of the cutting force in principal direction is studied by using wavelet packet decomposition and fast Fourier transform. The results show that the method can predict the steady cutting force accurately and reflect the amplitude frequency characteristics of the low frequency part for the cutting force in principal direction under different cutting parameters.

To accurately grasp the vibration stability of spiral groove dry gas seals (S-DGSs), the angular vibration stability thresholds of S-DGSs, which vary with the operating and structural parameters, were investigated by using carbon dioxide and hydrogen real gases as lubricants. The numerical results show that the vibration stability of the S-DGS in angular direction is independent of spring stiffness. Under the same conditions, the real gas effect enhances critical transverse moment of inertia and frequency ratio in carbon dioxide case, whereas it reduces both stability thresholds in hydrogen case. A spiral groove number Ng, land-to-groove ratio κ, and spiral angle δthat are too large or too small all contribute to an increased risk of S-DGS angular instability. By considering critical frequency ratio as the target, the optimal range of spiral groove structure parameters have been obtained by using a single factor analysis method.

The geometry of plastic gears used today is usually based on conventional steel gears, which are bound to the restrictions of the machining production of gears. The injection molding process provides more design freedom. This paper presents an approach to reduce the tooth root stress of plastic gears using a biologically inspired shape optimization method called CAO (Computer-Aided Optimization). CAO imitates the biological growth behavior from nature, such as bones or trees, which adapt to the load. It strengthens more heavily loaded areas of the surface and weakens less heavily loaded areas, resulting in an increase in load-bearing capacity. The simulation method is based on finite element analysis and considers the complex material behavior of short fiber reinforced plastics as well as the inhomogeneous fiber orientation. Object of the study are polymer gears made of polyamide 46 with and without short fiber reinforcement. By using the method presented here, it is possible to reduce the tooth root stress by up to 24% compared to a trochoidal tooth root with maximum rounding.

Improving the rigidity of machine tools for identifying the weak links of structural stiffness is one of the important issues in mechanical engineering. In this paper, a new weak index is proposed on a cantilever structure of the machine tool to identify the weak stiffness link. The weak index is a frequency parameter obtained via the vibration test method. In this method, the FRF coefficient of variation technique is proposed based on the FRF curvature method. The change of weak index is used to identify the weak link in the structural stiffness. The element stiffness weakening method that employs numerical examples of a cantilever beam and an elastic support beam is used to simulate the weak links of the stiffness. Compared with the FRF curvature ratio (FRF_CR) method, the FRF mutation coefficient is improved in the same frequency range. Moreover, the FRF_MCR indicator has more frequency points than the FRF_CR indicator in the same frequency range.

Due to low stiffness of compliant series robot body, the influence of joint flexible deformation caused by the gravity load of the end-effector on the absolute positioning accuracy cannot be ignored. In order to improve the flexible positioning accuracy of the robot end-effector, a calibration method for predicting and compensating the flexible positioning error of the 7-DOF series compliant robot due to the gravity load of the end-effector is proposed. The method identifies and predicts the pose configuration with similar flexible positioning error through the semi-parametric error model based on joint stiffness identification and of BP neural network. The feedforward method is used to compensate the positioning error. In this study, a 7-DOF series compliant robot is selected as the research object. Based on the principle of error similarity, the measurement points and the corresponding pose configurations are selected as the training data for the parameter identification of the semi-parametric error model, and the flexible positioning errors on the continuous trajectory of the end-effector are compensated according to the predicted values of the model. When the mass of the end-effector is 5 kg, by this method, the maximum value, mean value and mean square error of flexible positioning error on multiple straight-line trajectories on the plane are increased from 8.4779, 5.6039, and 1.8496 mm to 0.9720, 0.3079, and 0.2303 mm, respectively. It means the positioning accuracy are increased by 88.53%, 94.50%, and 87.55%, respectively, by which could observe that the precision of this robot’s end-effector was significantly improved.

As one of the important components of train traction motor, the bearing plays a key role in ensuring the safety of train operation. At present, the existing fault diagnosis methods for train traction motor bearings have the disadvantages of poor feature extraction ability, slow diagnosis speed, and low diagnosis accuracy. To solve the above problems, an improved deep residual network (IDRN) is proposed in this paper. Firstly, a new residual convolution block (RCB) is proposed to improve the extraction ability of hidden features. Secondly, the squeeze and excitation block (SE) is embedded in the residual block to increase the sensitivity of the model to features. Lastly, Adan is selected as the optimizer to increase the convergence speed of IDRN. The train traction motor bearing bench built by our research team is selected for the experiment. The results show that the test accuracy of IDRN on the bearing dataset of train traction motor is 98.72%, which is at least 2.27% higher than other comparative models. The IDRN model converges with fewer iterations in the training process, shortening the entire experiment time. At the same time, the CWRU bearing dataset and the bearing dataset with natural defects are selected for comparative verification. The experimental results show that the IDRN model exhibits strong robustness and practicability on different datasets.

Due to various nonlinear factors in an ordinary electromagnetic vibrator, the distortion of its output vibration waveform will always happen, especially at low frequencies (≤20 Hz), which blocks its application in a lot of area. To improve the acceleration waveform precision and reduce distortions at low frequencies, a waveform harmonic suppression method for low-frequency electromagnetic vibrators is proposed. After extracting the harmonic components in the output acceleration waveforms, a digital composite signal with harmonic compensation components is prospected according to the frequency response characteristic of the vibrator, and then sent back to drive the vibrator, which results in that the harmonic components in the formal waveform is suppressed. The proposed method was verified by simulations and experiments, and results show that the total harmonic distortions (THDs) of accelerations are reduced effectively at low frequencies, typically from 23% to less than 2% at the frequency as low as 0.1 Hz. The method is stable and robust because there is no real-time feedback loop in the system.

Advances in cleaner technologies have a critical role in reaching Europe’s climate and environmental goals. More precisely, in the case of the footwear bonding process its environmental impact is mainly related to the VOCs emissions resulting from the use of organic solvents in the most common adhesives used, as well as during the application of some surface treatments such as halogenation. Moreover, the use of raw materials of fossil origin also contributes to its carbon footprint. The aim of this work is to deploy cleaner technologies to minimise the environmental footprint of the footwear bonding process through several approaches at different steps of the process life cycle, also to contribute to footwear circularity. This work focuses on the synthesis and application of reactive hot melt polyurethanes from CO2-based polyols as biobased adhesives, and the study of plasma-based surface treatments (low-pressure plasma and atmospheric pressure plasma) to improve adhesion properties, using styrene-butadiene vulcanised (SBR) rubber as a representative footwear soling material. The influence of CO2-based polyols on the polyurethane structure and the physicochemical effects of the plasma treatments on the rubber surface, as well as the final adhesion properties have been evaluated by means of different experimental techniques. The results showed that the values obtained for the T-peel strength of the adhesive joints studied, with the combination of the application of the plasma surface treatments and the biobased reactive hotmelt, exceed the minimum quality requirements for footwear according to the standardised tests. As a result, the deployment of such cleaner technologies regarding adhesives and surface treatments in the footwear bonding process will contribute to improving footwear carbon footprint and its circularity.

Estimation of forging load in a closed-die forging process is important for process planners and designers. Physics-based models of the process require very high computational time as well as accurate input data. This work estimates the forging load by extracting the information from similar products in the shop floor. Accuracy of the estimate is optimized by means of a Kalman filter. A novel feature of this work is that instead of one deterministic estimate, three estimates, viz. lower, upper and most likely, are obtained. For demonstrating the efficacy of the proposed methodology, finite element method simulations using ABAQUS are used in lieu of real shop floor data. Six different products each having eight models are considered. Forging is supposed to be carried out with as well as without lubrication. In different cases, Kalman filtered most-likely estimate came very close to actual (FEM simulated) forging load and in no case deviation was more than 9%. The estimation error keeps on reducing with availability of data in an exponential manner. In an ideal case of no fluctuation in the measured actual (FEM simulated) forging load, error reduced from 30 to 5 kN after 7 data; further 13 data reduced the error to 1.7 kN. The interval of estimation (i.e. the difference between upper and lower estimates) also keeps on reducing with the availability of more data. For example, for an axisymmetric product, availability of 6 more data reduced the range of estimation from 62 to 25 kN. This establishes the efficacy of Kalman filter. In the proposed procedure the data is stored in an open source relational database management system, the MySQL, which can be retrieved easily. In Industry 4.0, shop floor data is easily available. Hence, the proposed method can be applied readily in real production shops.

In this paper, a potential technique is used to weld three sheets of AA 6082 through a two-step friction stir spot welding (TSFSSW). The optimal settings of the process parameters, namely, the rotational speed of the tool, dwell time, and plunge depth during welding have been analyzed. Taguchi’s L9 orthogonal array and ANOVA method is used to get proper material flow, appropriate heat conduction and the stir zone expansion, which helps in preparing sound joint. Microstructural tool analysis and fractography are performed by employing optical microscopy and Scanning Electron Microscopy (SEM). The tool was analyzed before and after use for heat effect along with the observation of the fracture behavior of the joint. To analyze the residual stresses developed in the joint, the XRD analysis is also carried out. The maximum tensile strength of 94.51 MPa was obtained under optimal parameters of the rotational speed of 1200 rpm, dwell time of 10 s, and plunge depth of 2.9 mm. The results of the ANFIS model revealed that a minor difference between experimental and model values (95.62) confirms the validation of the experiment. The resulting experimental findings of the ANFIS model were compared with other similar work done by researchers previously.

The problems of leakage, frictional wear, and flow heat transfer caused by the hysteresis characteristics of brush seals are prominent, and existing models for solving the hysteresis characteristics of brush seals have convergence difficulties owing to the extreme degree of nonlinearity caused by additional contacts. In this study, numerical models based on the finite element software ABAQUS were proposed to address the hysteresis characteristics of brush seals with three different structures: basic, low-lag hysteresis, and low-wear high-pressure bearing. The models accounted for the contacts between: the brush, brush and the baffle, and brush and the rotor, while damping was introduced to improve the convergence of the models. The hysteresis of the three structures under differential pressure was investigated and compared with theoretical calculations and experimental test results. The hysteresis of the bristles was normalised by the contact force, the shift of the contact area, and the contact friction force when the hysteresis effect occurred in the brush seal. The results show that the basic model has the most obvious hysteresis characteristics in the presence of differential pressure. Although the low-lag hysteresis model and the low-wear high-pressure bearing model have the weakest hysteresis effect, the deformation variables of the last row of bristles of these two structures are larger than those of the basic model; therefore, the contact position is prone to fatigue fracture. Simultaneously, the hysteresis effect was verified by varying the contact area and contact friction force, and it was found that the larger the contact area and contact friction force, the larger the hysteresis.

In many technological areas, especially in the medical sector, stainless steel parts are being used due to their longevity, good biocompatibility, and high resistance against hygrothermal conditions related to sterilization procedures. Numerous medical products include an adhesive bond that have to reliably withstand these harsh conditions encountered, for example, during autoclaving. However, well established adherent treatment procedures require hazardous chemicals or are not suitable for small fragile parts, for example, components of endoscopes. Therefore, efficient alternatives are necessary. This publication thus presents a combined surface treatment procedure of laser ablation/structuring and flame silicatization. The investigations demonstrate that the resistance to hygrothermal ageing of stainless steel adhesive joints can be significantly increased by pulsed laser irradiation. However, a drastic improvement can only be achieved when the laser fluence exceeds a certain threshold value and, in addition, a nanoporous oxide layer with a reduced chromium content is formed. For substrates of this surface type, ageing resistance can be increased even further by subsequent flame silicatization treatment. The combined methods have proven to be superior as compared to well established processes like sand blasting and coating or corundum blasting.

The present study aims to investigate the deep machining of Ti-6Al-4V alloy using a nanosecond (ns) laser through multi-pass and gas pressure. Experiments were conducted based on Full factorial design (FFD) by varying gas pressure and laser process parameters (LPP). Results showed that deeper grooves could be achieved through multi-pass laser scanning support with appropriate gas flow rate and laser parameters. A higher gas flow rate leads to more efficient removal of material and a faster machining rate. Further, the present findings revealed the substantial influence of laser power on the depth and width of the machined features, accounting for 41.28% and 7.11% of the variations, respectively. Moreover, power exhibited a significant impact on the taper angle (20.69%) and the heat-affected zone (HAZ) (12.04%) during the machining process. Additionally, the utilization of a multi-pass laser scan demonstrated a remarkable effect on the depth (1.89%), width (3.3%), HAZ (9.96%), and taper angle (8.78%). Furthermore, the assisted gas flow rate displayed a significant influence on the machined groove profile, that is, depth (41.97%), width (67.6%), HAZ (65.48%), and taper angle (30.15%). To achieve optimized results for high-depth machining with minimal defect, the present study recommends employing an average power of 40 W, an assisted gas flow rate of 25 L/min, and conducting four passes. These parameters develop laser machined surface with a high depth (~1499 µm) while simultaneously minimizing Taper (1.87°) and narrow HAZ (83 µm). Further, these conditions are suitable for laser cutting, trepanning, and surface texturing using a low-power laser system of Ti-6Al-4V alloy.

Flexible piezoelectric sensing arrays (FPSA) have an irreplaceable role in the fields of stress detection and self-energy supply and are part of the current hotspots of research in flexible electronics. In this paper, a FPSA with stable sensitivity and high duty cycle is designed to achieve high sensitivity over a wide range and a high duty cycle of 84.17%. The sensing unit uses two inverted trapezoidal prismatic structures (ITPS) with piezoelectric layers with stable sensitivity to pressure. For practical fabrication, a single-electrode array and cut package are proposed to solve the crosstalk problem between the highly duty cycle array units. The single-electrode array reduces the array structure’s complexity and the process’s difficulty. The cut package reduces crosstalk between units and improves the stress sensitivity of the array. Comsol Multiphysics and Abaqus provide strong validation and analysis of this design. The designed FPSA, which has demonstrated excellent performance in simulation analysis, significantly decreases the time and economic cost of device preparation. Given the compelling features, this study offers an effective solution for mitigating unit crosstalk in flexible sensing arrays, which hold significant academic research promise and application value.

With the rapid development of science and technology, exploration and study of extreme environments have advanced significantly. Consequently, the demand for equipment designed to operate under these conditions has increased. This paper proposes an innovative design method for stirring impeller structures based on the Teoriya Resheniya Izobreatatelskikh Zadatch (TRIZ) theory. By analyzing the interaction between components during the stirring process, we establish a TRIZ conflict resolution-based model for the innovative design process of stirring impeller structures. Our innovative design process is model-led, based on the TRIZ conflict resolution theory. This process improves existing stirrer structures to design a new type of stirrer with an ultra-thin multi-cross-shaped hole structure. We compare our proposed structural model to an existing stirrer using Computational Fluid Dynamics (CFD) for numerical simulation. The effect of different thicknesses, numbers of holes, radii, and shapes of the frame stirrer on the flow field values was analyzed. The results indicate that reducing the stirrer thickness, increasing the number of holes, and perforating the stirring impeller can enhance its stirring capacity. Changing the opening radius and adding special-shaped holes to the stirring impeller can also modify its stirring capacity. Ultimately, the proposed frame stirrer with an ultra-thin multi-cross-shaped hole structure increases the maximum turbulence kinetic energy by 14.6% and the maximum speed by 32.9% compared to the existing stirrer. Studying the feasibility of this innovative model and design method can provide new ideas for designing high-temperature and high-pressure reactor impellers in extreme environments.

In the present study, accumulative roll bonding is used to fabricate Al base composites with the thickness of 1 mm. then, fracture toughness, mechanical properties and forming limit diagrams (FLD) of them have been investigated versus ARB parameters experimentally. Boron nitride (BN) particles are used as reinforcements and Al/BN composites have been manufactured up to 10 accumulative rolling passes at 300°C. after the 10th pass, the strength of composite samples reached to 168 MPa registering 248% improvement than the initial AA1100 sample. Also, the bonding quality among the composite layers improved by increasing the number of passes. A uniform scattering of Boron nitride particles and bonding strength and quality was improved at higher number of passes. Moreover, the fracture mode at higher passes was observed as shear ductile that had been changed from deep dimples (for low number of passes). The area under the FLDs, dropped sharply after the first pass and then improved at higher passes, as the criterion of formability. Finally, fracture toughness enhanced to the maximum value of 30 MPam1/2for the composite samples fabricated with 10 passes.

The study focuses on an optimization study motivated by the increasing significance of shear-thickening fluids (STFs). We investigated the effects of parameters like additive surface area, additive ratio, and suspension temperature on outputs such as viscosity, thickening ratio, critical shear rate and thickening period of STFs using SiC as the additive. Enhancing STFs with SiC betters their stability and mechanical properties, ideal for industrial and defense applications. Our methodology has two steps. In the first step we developed a regression equation for each output by using some experimental data, then as the second step, each regression equation is used as an objective function and mathematical models are developed where the constraints represent the lower and upper bounds of the related inputs such as the surface area, amount of additive and, the surface area. Therefore, we want to obtain the best value of each input for each objective. The model’s results vary depending on the specific data and parameters used. This is a pioneering study employing both regression equations and mathematical models for this analysis.

In electrical discharge machining, the material removal phenomenon is heavily influenced by the breakdown strength of the dielectric fluid and the inter-electrode gap monitoring. This innovative research addresses a comparative performance evaluation and sustainability assessment between biodegradable palm oil and conventional EDM oil during machining of stainless steel (SS-316) using copper electrode. The cutting performance is investigated by comprehensive result analysis of various machinability aspects including material removal rate, surface integrity, tool wear rate, radial overcut of machined components. According to the findings, machining with palm oil dielectric outperformed the usual EDM oil with regards to improved material removal, surface morphology and finish, increased machined surface hardness with minimum surface crack density and hole overcut. Pyrolysis of conventional EDM dielectric oil leads to deposition of thin film carbon on bottom surface of the copper electrode which prevents the quick tool wear due to its higher breakdown voltage. The total machining cost expenditure per component under palm oil (INR383) is reduced by 11% than expenditure in traditional EDM oil (INR426). Compared to EDM oil, machining under biodegradable palm oil as dielectric fluid is better socio-economical viable and environmental conscious to enhance sustainability.

According to the nonlocal theory, the dynamic instability and vibration of functionally graded (FG) porous sandwich nanobeams resting on a visco-elastic foundation under axial harmonic load are studied. In this paper the Timoshenko and nonlocal continuum theory are employed to take shear deformation, rotational bending and small-scale effects into account. The governing equations of motion are extracted using the nonlinear Von-Karman, and Hamilton approaches. Then, to turn the partial differential equations (PDEs) into ordinary differential equations (ODEs) in the case of equations of motion, the method of Galerkin is employed, followed by the use of the multiple time scale method to solve the resulting equations. According to the results of this study, it can be claimed that the porosity ratio is more effective than porosity distribution and nonlocal parameters on the amplitude response and dynamic instability regions. Moreover, to examine thermal increments, foundation characteristics, slenderness, and thickness ratios, the bifurcation diagrams are drawn and discussed. It is found that foundation and geometric characteristics are of the highest significance in the nonlinear response of the Timoshenko nanobeams. The main intention of this study is to present a holistic idea about the porous materials used in sandwich structures which can be used in many composite structures in aircraft and automobiles.

This paper investigates the high-precision model-free control of robot manipulators. To this end, a model-free robust prescribed performance controller with an improved fast nonsingular terminal sliding mode surface (IFNTSM) and unknown system dynamics estimator (USDE) has been designed. An USDE method is employed to estimate model informations and further to achieve model-free control, which can avoid complex mathematical model calculation. Compared with some other model-free control methods like time-delay control (TDC) and neural-networks control (NNC), the USED does not require acceleration signal and is easy to implement. Then the prescribed performance control (PPC) has been used to limit error trajectory, which means the error can be pre-limit in a constraint band. A new transform function (TF) is designed for PPC, it has unlimited domain and can still maintain stability although tracking error will exceed PPC boundary sometimes, but the PPC with traditional TF will crash in this case. This is a great improvement for the stability of system compared with traditional TF. An improved fast nonsingular terminal sliding mode surface (IFNTSM) with a new adaptive law is proposed to accelerate convergence rate and improve steady-state accuracy on the sliding manifold. Finally, a practical finite-time controller (PFTC) has been constructed to drive sliding variable to a set centered on zero within a finite time, which means the convergence time can be calculated depending on the initial state. The transient response time can be shorten compared with traditional asymptotic stable. Abundant simulations and experimental results also verified the effectiveness of the proposed scheme.

In this work, the influence of hydrothermal ageing on performances of CFRP single lap bonded joints subjected to two types of pre-treatments was investigated. The first is a degreasing pre-treatment, while the second if a laser texturing pre-treatment through a CO2laser system. The study considered the influence of an aggressive environment on geometrical deviations and mechanical performances of the bonded joints. Measurements showed that adherends were more susceptible to water uptake after ageing, allowing an increase in laminate thickness of about 2.5%. Lap shear tests were carried out and a decrease in obtained mechanical performances was observed only for the degreased specimens, confirming the effectiveness of the adopted laser texturing to reduce ageing effects. Moreover, the proposed laser texturing pre-treatment for bonding is a sustainable process too because reduces the volume of the removed material efficiently with reduced costs.

This study investigates the mixing of non-Newtonian fluids in microfluidic devices using electrokinetic phenomena Micromixing is a crucial operation that finds multiple applications in chemical research and biomedical diagnostics. In order to improve mixing, multiple combinations of heterogeneously charged triangular elements are considered for investigation. The power-law model was used to characterize the non-Newtonian behavior of fluids. The effect of different geometrical parameters (hurdle length, height, number, and shape) and electrical parameters (applied external electric field and zeta potential on hurdles) on mixing are evaluated. The results indicate that the element shape, number, and fluid viscosity significantly affect mixing in microchannels. Moreover, the homogeneity of the mixed fluids increases with the flow behavior index (n). We found that dilatant fluids mix relatively better than pseudoplastic fluids. Finally, the Taguchi technique used to evaluate the combined effect of all factors and obtained optimal mixing conditions for various flow behavior indices (n) of non-Newtonian fluids.

Energy consumption has been a significant issue. CO2emissions have increased due to increased energy consumption. On the other hand, hard steels have been an essential subject of investigation due to their low energy consumption and good surface quality. Therefore, this experimental study investigates the effects of cutting parameters on cutting forces, power consumption (PC), energy consumption (EC), sound intensity (SI), and surface roughness (Ra) in machining AISI S1 (60 HRC) cold work tool steel. Feed rate (f) on cutting force with 53.23%, power consumption with 94.11% depth of cut (ap), energy efficiency with 74.92% feed rate, over surface roughness value with 86.66%, depth of cut with 94.42% on sound intensity are effective parameters. Mathematical equations related to the cutting parameters were obtained. In addition, mathematical equations were created between cutting force and power consumption, cutting force and sound intensity, and power consumption and sound intensity. Finally, optimum cutting conditions were determined with multiple optimisation methods, which turned out to be 210 m/min cutting speed (v), 0.08 mm cutting depth, and 0.0505 mm/rev feed rate. Accordingly, it was calculated that sound intensity would be reduced by 4.25%, surface roughness value would be decreased by 36.36%, power consumption by 21.74%, Fzby 26.77%, by Fy52.46% and Fxby 24.44%.

This paper aims to obtain an analytical solution for free vibration and stability analysis of shallow curved sandwich panels made of a porous metal-foam core and nanocomposites reinforced sheets resting on a Winkler-Pasternak elastic foundation. In this regard, two nanocomposites, carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are considered for reinforcing the face-sheets. The governing equations are developed by considering the transversal shear strains based on the first-order shear deformation theory (FSDT). The obtained system of differential equations representing the dynamic equilibrium and compatibility of the proposed curved sandwich panels are solved analytically, using the principal of Galerkin method. In order to examine the results of developed formulation, some benchmark examples are adopted from the existing literature and the obtained results corresponding to the considered examples are compared with those are presented in the references. Using the achieved numerical results in the framework of a comprehensive parametric study, the effects of various material and geometrical factors and also various boundary conditions on the natural frequencies and buckling loads of the proposed sandwich panels are assessed. By performing the extensive parametric study it was observed that several results corresponding to the free vibration and stability of the proposed sandwich panels can be achieved by the present method without spending much time for computations. On the contrary, in order to achieve the similar results using the numerical methods, a time-consuming process is required which can justify the novelty of the present work.

The inclination angle is an important factor for slope deformation monitoring. This paper introduces a self-powered pendulum inclination sensor (PI-TENG) based on triboelectric nanogenerator, which can effectively monitor slope deformation. PI-TENG adopts raster-sliding mode as the main structure. The fabricated PI-TENG, based on a raster-sliding working mode, using the linear relationship between the rotation angle of the monitoring object and the number of output pulses to establish an intuitive rotation signal mapping, which can realize self-powered monitoring of the rotation direction and angle not being affected by the environment (such as temperature and humidity). The corresponding minimum resolution of PI-TENG is 3° and can be further improved by increasing the number of Nylon grids on the stator. Importantly, the sensor has a simple structure and low price, and can realize self-powered monitoring without additional power supply. This work provides new ideas for monitoring slope deformation and early warning of landslides.

Machining is a complex process between the cutting tool and the workpiece, and in this process, the cutting tool constantly wears out with various wear mechanisms. Tool-wear estimation in turning is a complicated process; thus, there is a need for a study to reveal the time-dependent behavior of tool wear. In this study, tool wear and surface roughness change during the turning process of AISI 4140 steel at low cutting speeds were examined in detail with variable feed values for the first time. For this purpose, a half-minute cutting time was applied for each pass to analyze the tool wear as gradually as possible. Tool wear (flank, notch, and nose), surface roughness (Ra, Rz, and Rt), and chip morphologies were examined after each turning operation. The flank wear reached 0.3 mm, which is one of the tool life criteria according to ISO 3685, and the experiments were terminated at the 149th minute. Initially, a significant surface improvement (approx. 300%) was observed due to the decrease in feed values. In subsequent experiments, the effect of feed was significantly reduced due to increased tool wear, and limited surface roughness improvement (approx. 30%) was observed. At the beginning of the experiment, the chip breaker function of the cutting insert was successful at almost all feeds. However, in subsequent experiments, it was found that even at higher feeds, the chip breaker geometry of the insert deteriorated due to tool wear, causing changes in chip morphology, and resulting in long and undesirable chips.

Piezoelectric energy harvesting from rotational motions currently receives attention as a clean and permanent energy source. However, because of low output power, optimizing and improving the efficiency of this strategy through different methods is of great importance. This study investigates a new high-efficiency piezoelectric energy harvester under rotational indirect magnetic excitation using frequency up-conversion. The studied piezoelectric energy harvester is composed of an exponentially tapered cantilever beam with a piezoelectric layer, excited magnets, a tip mass, an octagonal disk attached to the rotating shaft, and exciting magnets on the disk. The potential energy and nonlinear magnetic force are determined and substituted into an electromechanically coupled governing equation after derivation. Numerical methods are applied to solve the governing equations due to their nonlinear nature and periodic oscillations. The tip mass varies to maintain a constant natural frequency and cancel out the effect of concurrent variations of the natural frequency and tapering parameter. Verification of the theoretical model is performed by the finite element and experiment methods. The effects of some parameters, such as the tapering parameter, total resistance of the circuit, number of magnets, and rotational speed, on the output voltage and power densities are evaluated. Results show a fourfold increase in output power density when comparing exponentially tapered width to constant width. Finally, frequency response curves are plotted and analyzed to examine the effect of shaft rotational speed, subharmonics, and bandwidth. The most important result extracted from the frequency response diagram is the increase in the number of subharmonics and the observation of 2ω/5 and 2ω/7 subharmonic components in the frequency response of the harvester with exponentially tapered width.

This paper strives to compare between two 3-Degree of Freedom (DoF) Spatial Parallel Manipulators (SPMs) belonging to the 3-[PP]S-Y family viz., 3-RRS and 3-RPS. The planes of the manipulators belong to this family are arranged in a Y-pattern such that they intersect at 120° in a common line. Both of these manipulators have a common motion of 1T2R (T: Translation, R: Rotation) type, and their comparison in this work is carried out by considering the effects of link tolerance and parasitic motions, for the same task space and End-Effector (EE) positions. Their respective position kinematic analysis is discussed initially. The comparison is then carried out by considering two different cases based on the sizes of the moving platform relative to the base platform. The errors are quantified and all the comparative results are represented with the aid of plots. The conclusions are summarized at the end that allow to know the better of the two manipulators for the given effects.

Sandwich panels with pyramidal cores made of thin-walled tubes absorb energy very well, but their main limitation is the complexity of producing such a structure. This study utilized a novel self-interlocking assembly technique to fabricate the lattice core, significantly reducing fabrication time and material requirements. Experimental tests and finite element analyses were performed to investigate the effect of geometrical parameters on the out-of-plane characteristics of sandwich panels with pyramidal thin-walled tube cores and relative densities ranging from 1.39% to 3.96%. Finite element predictions for deformation mechanisms, compressive strength, and energy absorption match experimental results. The results reveal that the proposed approach for producing the nodes worked successfully, with no brazed nodes breaking. The amount of energy absorbed per unit of mass reduces by 22% and 27%, respectively, when the slenderness is increased from 3 to 5 and subsequently from 5 to 7. In addition, when the angle of the tubes is increased from 50° to 55°, it makes them 23% stronger and absorbs 13% more energy per unit mass. Regarding strength and energy absorption per unit volume, pyramidal thin-walled tube cores are better than traditional lightweight sandwich panels, especially at lower relative densities.

A combined experimental and theoretical study on thermal conductivity, heat transfer specific heat, and electronic properties has been done for doped CeO2/water nanofluid. First, the sol-gel method was implemented for the synthesis of doped CeO2nanoparticles and then a mixture of nanoparticles with different concentrations of nanofluid. X-ray diffraction and SEM analysis confirm the structural phase purity and homogeneous mixing of nanofluids. Experimental thermal conductivity and specific heat of pure and 4f-doped CeO2were estimated and found very close to our theoretical calculations. Experimental investigations have been carried out for the measurement of heat transfer using pure and doped CeO2/water nanofluid as the coolant. The experiments were aimed at determining the heat transfer and other thermal properties with different concentrations and with various fluid with Reynolds number 2500 and 3500. The heat transfer coefficient of nanofluids increases not only with an increase in the volume flow rate of the hot water but also increases with increase in the atomic number of dopant elements in CeO2. Electronic states show variation in band gap with doping which may also play an important role in the improvement of solar collectors. It is clear from experimental and theoretical findings that the thermal and electronic properties depend on number of valance electrons. Hence doping of 4f-element in CeO2plays a vital role to increase the thermal conductivity and tuning of electronic properties leads to many applications in thermal sensors and solar cell-based industries.

The laser ultrasonic composite cutting (LUCC) process was proposed by combining laser heating-assisted cutting (LHAC) and elliptical ultrasonic vibration cutting (UVC). In the process of cutting experiment, cubic boron nitride (CBN) is selected as the tool’s material. The wear morphology and wear appearance of the tools were observed by super depth-of-field microscopy and scanning electron microscopy (SEM) to research the wear characteristics and wear mechanism of CBN tools during LUCC of cemented carbide. Compared with conventional cutting (CC), UVC and LHAC, during LUCC of cemented carbide with CBN tools the tool wear are significantly reduced by 45.11%, 28.92%, and 17.39% respectively, the cutting force are decreased by 61%, 44%, and 46% respectively, and the surface roughness are lowered by 77%, 55%, and 62% respectively, therefore the tool life is obviously lengthened. Moreover, the tool flank wears model of during LUCC of cemented carbide was established and verified by the tool flank face wear test. The results show that when the CBN tool is used for LUCC of cemented carbide, the wear band on the tool’s rake face is basically parallel to the cutting edge and is in the shape of a long strip, and the wear band on the tool’s flank face shows a triangular-shaped wear band accompanied by shallow pits and grooves; In the process of the LUCC of cemented carbide, the main causes of CBN tool wear include adhesive wear, oxidation wear and abrasive wear are the main causes of CBN tool wear during LUCC of cemented carbide; The faster the cutting speed, the bigger the error among the experimental value with the calculated value, and the wear of tool’s flank face during LUCC of cemented carbide gradually increased.

Compact size of the heat exchange module is an important design consideration in majority of the thermal management systems. Using winglet type vortex generators, a sizeable improvement in the compactness of a widely used finned-tube array is attempted through this study. Since the degree of thermal augmentation changes with the generators’ position, around the tubes, this 3D comprehensive computational investigation aims to develop phenomenological correlations for the positional optimization, which are applicable over a wide range of operating conditions. Besides, this article is dedicated to understanding different aspects of the augmentation mechanism, including the tube-wake management and the performance improvement caused by the best design(s). Based on a parametric investigation, designs that are best suited for obtaining a sizeable performance augmentation of the system are identified. Furthermore, a critical assessment of the best designs is carried out to evaluate their impact on the heat transfer from wake-affected surfaces, both fins and tubes. It is encouraging to observe that the wake-affected surfaces also experience sizeable thermal augmentation, which increases further with the Reynolds number. While the total fin surface experiences a highest Colburn j-factor augmentation of 53.6%, the wake-affected fin undergoes 205.1% rise. An evident manifestation of the augmented Colburn j-factor is the reformed temperature distribution, which bears lower values all over the fins.

The gas turbine is one of the most suitable equipment for various applications. Usually, a gas turbine comprises a set of discs to maintain turbine blades. The rotating disc in gas turbines is one of the critical components affected by various thermal and mechanical loads. The current article considers a new rotating disc with variable thickness (power-law profile). The functionally graded material has been used as the disc material, and the disc’s properties vary with temperature and location. Therefore, the mechanical and thermal behaviours of the disc are a function of temperature and location. The differential energy balance equation has been derived for analysing the new disc. In the performed analysis, the conduction and convection heat transfer coefficients vary with temperature and location; thus, the derived final heat transfer equation has high nonlinearity. One of the efficient expansion methods, the so-called Differential Transformation Method (DTM), is used for the governed equation’s analytical solution, and the numerical solution is used for validation. Then, the stress analysis is performed using analytical expressions according to the temperature profile. The impacts of geometrical and thermophysical characteristics on the temperature and stress distribution are evaluated using the analytical solution in the new disc. The comparison of displacement and stresses in the new FGM disc and old discs shows that the thermo-mechanical performance of the new proposed disc is improved significantly.

The electronic industry’s shift towards multicore processor technology which leads to an increase the power densities of the chip. In multicore processors the hotpot location arises depending on the computational load which leads to the generating the non-uniform heat flux. The uneven cooling of a multicore processor will affect the reliability and life span of the chip. In this study, employed parallel microchannel cooling systems (PMCHS) with different flow configurations by numerical simulations. The objective of the present work is to investigate the thermos-hydrodynamic characteristics of a PMCHS under a non-uniform heat load, the heat load is considered from an actively running 8-core processor. Here, considered that three types different flow configurations (U, I and Z) to determine the flow maldistribution, in additions the thermal performance of each flow configuration was analysed at non-uniform heat conditions. The size and shape of the PMCHS is equal to the octa-core processor which has been mimicked, and real-time heat load data of the processor has been retrieved. The present study exhibits that non-uniform thermal load creates additional non-uniform temperature distribution along with flow maldistribution in the PMCHS. Each flow configuration has a different flow maldistribution pattern, whereas the sometimes intended flow maldistribution helps to give better uniform cooling on the chip.

Epoxy coatings of floors are a very good solution for car repair workshops. Epoxy coatings provide the floor with resistance to oil, fuel, and grease staining. The floor surface is very easy to clean. To support sustainable development, a filler in the form of waste granite powder was added to the epoxy coating. In a car repair workshop, an epoxy coating of the floor was made according to the recipe previously developed in laboratory tests. The pull-off strength of the concrete substrate was tested before and after the mechanical treatment of concrete surface. The pull-off strength of the epoxy coating was also tested. The obtained results were compared with the laboratory results. It has been proved that the waste granite filler does not deteriorate the pull-off strength of the epoxy coating and thus its durability. The waste granite powder can be successfully applied as a filler in real epoxy coatings of floors.

The widespread deployment of fuel cell technology requires the development of new manufacturing technologies to turn it economically viable. Stencil printing is known as one of the highest throughput techniques for applying adhesives, where a moving squeegee forces the adhesive through pre-defined apertures in a stencil onto a substrate. Thus, stencil printing is investigated as an innovative method to reduce production costs and manufacturing cycle times of fuel cell sealings. Moreover, in order to allow a greater design freedom, adhesive layer thicknesses up to 500 µm should be printable under reproducible conditions and within cycle times <3 s, which have not been realized or implemented until today. With the aim of printing closed-loop structures (sealings), a mesh located on the upper region of the aperture needs to be integrated. However, this mesh can produce additional air bubbles and surface irregularities, which might affect the sealing performance and diminish the process stability. This paper describes the experimentally identified formation mechanisms of bubbles during the separation step. The quantity and size of these bubbles were measured for five separation speeds, two mesh opening sizes and three adhesive systems (UV-curable acrylic). Primary focus was placed on relating the print results with the adhesive rheological properties, which are decisive to successfully implement the sealing application process. It was found that a previously derived empirical relationship to predict the adhesive tendency to stretch filaments can be employed as a model to quantitatively assess the characteristics of bubbles that emerge during the separation step and thus specify rheological properties to enhance print quality.